It alleges a 2010 operation in Afghanistan was a retaliation to the killing of a New Zealand soldier, and could have involved war crimes.

Mr Hager told Mike Hosking he heard there was a mood of rage about the operation.

"For the SAS to be in a town and be burning down and blowing up houses while they went around is not normal. They normally race into a place and creep into a place. There was something about this that was seriously abnormal."

Mr Hager said the Defence Force needs to allow an independent inquiry to keep its reputation clean.

"The New Zealand military prides itself constantly of being different from other militaries like the United States," he said.

Intelligence analyst Paul Buchanan told Mike Hosking if the New Zealand Defence Force stands by its soldiers, it should allow the independent inquiry.

"The NZDF has maintained all along that Hager and Stephenson are out to get them. If in fact the SAS operated professionally, then this will exonerate the NZDF and will justify their criticism of these authors."